import * as dingbatToUnicode from 'dingbat-to-unicode';
import _ from 'underscore';

import * as documents from '../documents';
import { Result } from '../results';
import { warning} from '../results';
import * as xml from '../xml';
import * as transforms from '../transforms';
import * as uris from './uris';

function createBodyReader(options) {
    return {
        readXmlElement: function(element) {
            return new BodyReader(options).readXmlElement(element);
        },
        readXmlElements: function(elements) {
            return new BodyReader(options).readXmlElements(elements);
        }
    };
}

function BodyReader(options) {
    var complexFieldStack = [];
    var currentInstrText = [];

    // When a paragraph is marked as deleted, its contents should be combined
    // with the following paragraph. See 17.13.5.15 del (Deleted Paragraph) of
    // ECMA-376 4th edition Part 1.
    var deletedParagraphContents = [];

    var relationships = options.relationships;
    var contentTypes = options.contentTypes;
    var docxFile = options.docxFile;
    var files = options.files;
    var numbering = options.numbering;
    var styles = options.styles;

    function readXmlElements(elements) {
        var results = elements.map(readXmlElement);
        return combineResults(results);
    }

    function readXmlElement(element) {
        if (element.type === "element") {
            var handler = xmlElementReaders[element.name];
            if (handler) {
                return handler(element);
            } else if (!Object.prototype.hasOwnProperty.call(ignoreElements, element.name)) {
                var message = warning("An unrecognised element was ignored: " + element.name);
                return emptyResultWithMessages([message]);
            }
        }
        return emptyResult();
    }

    function readParagraphProperties(element) {
        return readParagraphStyle(element).map(function(style) {
            return {
                type: "paragraphProperties",
                styleId: style.styleId,
                styleName: style.name,
                alignment: element.firstOrEmpty("w:jc").attributes["w:val"],
                numbering: readNumberingProperties(style.styleId, element.firstOrEmpty("w:numPr"), numbering),
                indent: readParagraphIndent(element.firstOrEmpty("w:ind"))
            };
        });
    }

    function readParagraphIndent(element) {
        return {
            start: element.attributes["w:start"] || element.attributes["w:left"],
            end: element.attributes["w:end"] || element.attributes["w:right"],
            firstLine: element.attributes["w:firstLine"],
            hanging: element.attributes["w:hanging"]
        };
    }

    function readRunProperties(element) {
        return readRunStyle(element).map(function(style) {
            var fontSizeString = element.firstOrEmpty("w:sz").attributes["w:val"];
            // w:sz gives the font size in half points, so halve the value to get the size in points
            var fontSize = /^[0-9]+$/.test(fontSizeString) ? parseInt(fontSizeString, 10) / 2 : null;

            return {
                type: "runProperties",
                styleId: style.styleId,
                styleName: style.name,
                verticalAlignment: element.firstOrEmpty("w:vertAlign").attributes["w:val"],
                font: element.firstOrEmpty("w:rFonts").attributes["w:ascii"],
                fontSize: fontSize,
                isBold: readBooleanElement(element.first("w:b")),
                isUnderline: readUnderline(element.first("w:u")),
                isItalic: readBooleanElement(element.first("w:i")),
                isStrikethrough: readBooleanElement(element.first("w:strike")),
                isAllCaps: readBooleanElement(element.first("w:caps")),
                isSmallCaps: readBooleanElement(element.first("w:smallCaps")),
                highlight: readHighlightValue(element.firstOrEmpty("w:highlight").attributes["w:val"])
            };
        });
    }

    function readUnderline(element) {
        if (element) {
            var value = element.attributes["w:val"];
            return value !== undefined && value !== "false" && value !== "0" && value !== "none";
        } else {
            return false;
        }
    }

    function readBooleanElement(element) {
        if (element) {
            var value = element.attributes["w:val"];
            return value !== "false" && value !== "0";
        } else {
            return false;
        }
    }

    function readBooleanAttributeValue(value) {
        return value !== "false" && value !== "0";
    }

    function readHighlightValue(value) {
        if (!value || value === "none") {
            return null;
        } else {
            return value;
        }
    }

    function readParagraphStyle(element) {
        return readStyle(element, "w:pStyle", "Paragraph", styles.findParagraphStyleById);
    }

    function readRunStyle(element) {
        return readStyle(element, "w:rStyle", "Run", styles.findCharacterStyleById);
    }

    function readTableStyle(element) {
        return readStyle(element, "w:tblStyle", "Table", styles.findTableStyleById);
    }

    function readStyle(element, styleTagName, styleType, findStyleById) {
        var messages = [];
        var styleElement = element.first(styleTagName);
        var styleId = null;
        var name = null;
        if (styleElement) {
            styleId = styleElement.attributes["w:val"];
            if (styleId) {
                var style = findStyleById(styleId);
                if (style) {
                    name = style.name;
                } else {
                    messages.push(undefinedStyleWarning(styleType, styleId));
                }
            }
        }
        return elementResultWithMessages({styleId: styleId, name: name}, messages);
    }

    function readFldChar(element) {
        var type = element.attributes["w:fldCharType"];
        if (type === "begin") {
            complexFieldStack.push({type: "begin", fldChar: element});
            currentInstrText = [];
        } else if (type === "end") {
            var complexFieldEnd = complexFieldStack.pop();
            if (complexFieldEnd.type === "begin") {
                complexFieldEnd = parseCurrentInstrText(complexFieldEnd);
            }
            if (complexFieldEnd.type === "checkbox") {
                return elementResult(documents.checkbox({
                    checked: complexFieldEnd.checked
                }));
            }
        } else if (type === "separate") {
            var complexFieldSeparate = complexFieldStack.pop();
            var complexField = parseCurrentInstrText(complexFieldSeparate);
            complexFieldStack.push(complexField);
        }
        return emptyResult();
    }

    function currentHyperlinkOptions() {
        var topHyperlink = _.last(complexFieldStack.filter(function(complexField) {
            return complexField.type === "hyperlink";
        }));
        return topHyperlink ? topHyperlink.options : null;
    }

    function parseCurrentInstrText(complexField) {
        return parseInstrText(
            currentInstrText.join(''),
            complexField.type === "begin"
                ? complexField.fldChar
                : xml.emptyElement
        );
    }

    function parseInstrText(instrText, fldChar) {
        var externalLinkResult = /\s*HYPERLINK "(.*)"/.exec(instrText);
        if (externalLinkResult) {
            return {type: "hyperlink", options: {href: externalLinkResult[1]}};
        }

        var internalLinkResult = /\s*HYPERLINK\s+\\l\s+"(.*)"/.exec(instrText);
        if (internalLinkResult) {
            return {type: "hyperlink", options: {anchor: internalLinkResult[1]}};
        }

        var checkboxResult = /\s*FORMCHECKBOX\s*/.exec(instrText);
        if (checkboxResult) {
            var checkboxElement = fldChar
                .firstOrEmpty("w:ffData")
                .firstOrEmpty("w:checkBox");
            var checkedElement = checkboxElement.first("w:checked");
            var checked = checkedElement == null
                ? readBooleanElement(checkboxElement.first("w:default"))
                : readBooleanElement(checkedElement);
            return {type: "checkbox", checked: checked};
        }

        return {type: "unknown"};
    }

    function readInstrText(element) {
        currentInstrText.push(element.text());
        return emptyResult();
    }

    function readSymbol(element) {
        // See 17.3.3.30 sym (Symbol Character) of ECMA-376 4th edition Part 1
        var font = element.attributes["w:font"];
        var char = element.attributes["w:char"];
        var unicodeCharacter = dingbatToUnicode.hex(font, char);
        if (unicodeCharacter == null && /^F0..$/.test(char)) {
            unicodeCharacter = dingbatToUnicode.hex(font, char.substring(2));
        }

        if (unicodeCharacter == null) {
            return emptyResultWithMessages([warning(
                "A w:sym element with an unsupported character was ignored: char " +  char + " in font " + font
            )]);
        } else {
            return elementResult(new documents.Text(unicodeCharacter.string));
        }
    }

    function noteReferenceReader(noteType) {
        return function(element) {
            var noteId = element.attributes["w:id"];
            return elementResult(new documents.NoteReference({
                noteType: noteType,
                noteId: noteId
            }));
        };
    }

    function readCommentReference(element) {
        return elementResult(documents.commentReference({
            commentId: element.attributes["w:id"]
        }));
    }

    function readChildElements(element) {
        return readXmlElements(element.children);
    }

    var xmlElementReaders = {
        "w:p": function(element) {
            var paragraphPropertiesElement = element.firstOrEmpty("w:pPr");

            var isDeleted = !!paragraphPropertiesElement
                .firstOrEmpty("w:rPr")
                .first("w:del");

            if (isDeleted) {
                element.children.forEach(function(child) {
                    deletedParagraphContents.push(child);
                });
                return emptyResult();
            } else {
                var childrenXml = element.children;
                if (deletedParagraphContents.length > 0) {
                    childrenXml = deletedParagraphContents.concat(childrenXml);
                    deletedParagraphContents = [];
                }
                return ReadResult.map(
                    readParagraphProperties(paragraphPropertiesElement),
                    readXmlElements(childrenXml),
                    function(properties, children) {
                        return new documents.Paragraph(children, properties);
                    }
                ).insertExtra();
            }
        },
        "w:r": function(element) {
            return ReadResult.map(
                readRunProperties(element.firstOrEmpty("w:rPr")),
                readXmlElements(element.children),
                function(properties, children) {
                    var hyperlinkOptions = currentHyperlinkOptions();
                    if (hyperlinkOptions !== null) {
                        children = [new documents.Hyperlink(children, hyperlinkOptions)];
                    }

                    return new documents.Run(children, properties);
                }
            );
        },
        "w:fldChar": readFldChar,
        "w:instrText": readInstrText,
        "w:t": function(element) {
            return elementResult(new documents.Text(element.text()));
        },
        "w:tab": function(element) {
            return elementResult(new documents.Tab());
        },
        "w:noBreakHyphen": function() {
            return elementResult(new documents.Text("\u2011"));
        },
        "w:softHyphen": function(element) {
            return elementResult(new documents.Text("\u00AD"));
        },
        "w:sym": readSymbol,
        "w:hyperlink": function(element) {
            var relationshipId = element.attributes["r:id"];
            var anchor = element.attributes["w:anchor"];
            return readXmlElements(element.children).map(function(children) {
                function create(options) {
                    var targetFrame = element.attributes["w:tgtFrame"] || null;

                    return new documents.Hyperlink(
                        children,
                        _.extend({targetFrame: targetFrame}, options)
                    );
                }

                if (relationshipId) {
                    var href = relationships.findTargetByRelationshipId(relationshipId);
                    if (anchor) {
                        href = uris.replaceFragment(href, anchor);
                    }
                    return create({href: href});
                } else if (anchor) {
                    return create({anchor: anchor});
                } else {
                    return children;
                }
            });
        },
        "w:tbl": readTable,
        "w:tr": readTableRow,
        "w:tc": readTableCell,
        "w:footnoteReference": noteReferenceReader("footnote"),
        "w:endnoteReference": noteReferenceReader("endnote"),
        "w:commentReference": readCommentReference,
        "w:br": function(element) {
            var breakType = element.attributes["w:type"];
            if (breakType == null || breakType === "textWrapping") {
                return elementResult(documents.lineBreak);
            } else if (breakType === "page") {
                return elementResult(documents.pageBreak);
            } else if (breakType === "column") {
                return elementResult(documents.columnBreak);
            } else {
                return emptyResultWithMessages([warning("Unsupported break type: " + breakType)]);
            }
        },
        "w:bookmarkStart": function(element){
            var name = element.attributes["w:name"];
            if (name === "_GoBack") {
                return emptyResult();
            } else {
                return elementResult(new documents.BookmarkStart({name: name}));
            }
        },

        "mc:AlternateContent": function(element) {
            return readChildElements(element.firstOrEmpty("mc:Fallback"));
        },

        "w:sdt": function(element) {
            var contentResult = readXmlElements(element.firstOrEmpty("w:sdtContent").children);
            return contentResult.map(function(content) {
                // From the WordML standard: https://learn.microsoft.com/en-us/openspecs/office_standards/ms-docx/3350cb64-931f-41f7-8824-f18b2568ce66
                //
                // > A CT_SdtCheckbox element that specifies that the parent
                // > structured document tag is a checkbox when displayed in the
                // > document. The parent structured document tag contents MUST
                // > contain a single character and optionally an additional
                // > character in a deleted run.

                var checkbox = element
                    .firstOrEmpty("w:sdtPr")
                    .first("wordml:checkbox");

                if (checkbox) {
                    var checkedElement = checkbox.first("wordml:checked");
                    var isChecked = !!checkedElement && readBooleanAttributeValue(
                        checkedElement.attributes["wordml:val"]
                    );
                    var documentCheckbox = documents.checkbox({
                        checked: isChecked
                    });

                    var hasCheckbox = false;
                    var replacedContent = content.map(transforms._elementsOfType(
                        documents.types.text,
                        function(text) {
                            if (text.value.length > 0 && !hasCheckbox) {
                                hasCheckbox = true;
                                return documentCheckbox;
                            } else {
                                return text;
                            }
                        }
                    ));

                    if (hasCheckbox) {
                        return replacedContent;
                    } else {
                        return documentCheckbox;
                    }

                } else {
                    return content;
                }
            });
        },

        "w:ins": readChildElements,
        "w:object": readChildElements,
        "w:smartTag": readChildElements,
        "w:drawing": readChildElements,
        "w:pict": function(element) {
            return readChildElements(element).toExtra();
        },
        "v:roundrect": readChildElements,
        "v:shape": readChildElements,
        "v:textbox": readChildElements,
        "w:txbxContent": readChildElements,
        "wp:inline": readDrawingElement,
        "wp:anchor": readDrawingElement,
        "v:imagedata": readImageData,
        "v:group": readChildElements,
        "v:rect": readChildElements
    };

    return {
        readXmlElement: readXmlElement,
        readXmlElements: readXmlElements
    };


    function readTable(element) {
        var propertiesResult = readTableProperties(element.firstOrEmpty("w:tblPr"));
        return readXmlElements(element.children)
            .flatMap(calculateRowSpans)
            .flatMap(function(children) {
                return propertiesResult.map(function(properties) {
                    return documents.Table(children, properties);
                });
            });
    }

    function readTableProperties(element) {
        return readTableStyle(element).map(function(style) {
            return {
                styleId: style.styleId,
                styleName: style.name
            };
        });
    }

    function readTableRow(element) {
        var properties = element.firstOrEmpty("w:trPr");

        // See 17.13.5.12 del (Deleted Table Row) of ECMA-376 4th edition Part 1
        var isDeleted = !!properties.first("w:del");
        if (isDeleted) {
            return emptyResult();
        }

        var isHeader = !!properties.first("w:tblHeader");
        return readXmlElements(element.children).map(function(children) {
            return documents.TableRow(children, {isHeader: isHeader});
        });
    }

    function readTableCell(element) {
        return readXmlElements(element.children).map(function(children) {
            var properties = element.firstOrEmpty("w:tcPr");

            var gridSpan = properties.firstOrEmpty("w:gridSpan").attributes["w:val"];
            var colSpan = gridSpan ? parseInt(gridSpan, 10) : 1;

            var cell = documents.TableCell(children, {colSpan: colSpan});
            cell._vMerge = readVMerge(properties);
            return cell;
        });
    }

    function readVMerge(properties) {
        var element = properties.first("w:vMerge");
        if (element) {
            var val = element.attributes["w:val"];
            return val === "continue" || !val;
        } else {
            return null;
        }
    }

    function calculateRowSpans(rows) {
        var unexpectedNonRows = _.any(rows, function(row) {
            return row.type !== documents.types.tableRow;
        });
        if (unexpectedNonRows) {
            removeVMergeProperties(rows);
            return elementResultWithMessages(rows, [warning(
                "unexpected non-row element in table, cell merging may be incorrect"
            )]);
        }
        var unexpectedNonCells = _.any(rows, function(row) {
            return _.any(row.children, function(cell) {
                return cell.type !== documents.types.tableCell;
            });
        });
        if (unexpectedNonCells) {
            removeVMergeProperties(rows);
            return elementResultWithMessages(rows, [warning(
                "unexpected non-cell element in table row, cell merging may be incorrect"
            )]);
        }

        var columns = {};

        rows.forEach(function(row) {
            var cellIndex = 0;
            row.children.forEach(function(cell) {
                if (cell._vMerge && columns[cellIndex]) {
                    columns[cellIndex].rowSpan++;
                } else {
                    columns[cellIndex] = cell;
                    cell._vMerge = false;
                }
                cellIndex += cell.colSpan;
            });
        });

        rows.forEach(function(row) {
            row.children = row.children.filter(function(cell) {
                return !cell._vMerge;
            });
            row.children.forEach(function(cell) {
                delete cell._vMerge;
            });
        });

        return elementResult(rows);
    }

    function removeVMergeProperties(rows) {
        rows.forEach(function(row) {
            var cells = transforms.getDescendantsOfType(row, documents.types.tableCell);
            cells.forEach(function(cell) {
                delete cell._vMerge;
            });
        });
    }

    function readDrawingElement(element) {
        var blips = element
            .getElementsByTagName("a:graphic")
            .getElementsByTagName("a:graphicData")
            .getElementsByTagName("pic:pic")
            .getElementsByTagName("pic:blipFill")
            .getElementsByTagName("a:blip");

        return combineResults(blips.map(readBlip.bind(null, element)));
    }

    function readBlip(element, blip) {
        var propertiesElement = element.firstOrEmpty("wp:docPr");
        var properties = propertiesElement.attributes;

        var altText = isBlank(properties.descr) ? properties.title : properties.descr;

        var blipImageFile = findBlipImageFile(blip);
        if (blipImageFile === null) {
            return emptyResultWithMessages([warning("Could not find image file for a:blip element")]);
        }

        return readImage(blipImageFile, altText).map(function(imageElement) {
            var hlinkClickElement = propertiesElement.firstOrEmpty("a:hlinkClick");
            var relationshipId = hlinkClickElement.attributes["r:id"];
            if (relationshipId) {
                var href = relationships.findTargetByRelationshipId(relationshipId);
                return new documents.Hyperlink([imageElement], {href: href});
            } else {
                return imageElement;
            }
        });
    }

    function isBlank(value) {
        return value == null || /^\s*$/.test(value);
    }

    function findBlipImageFile(blip) {
        var embedRelationshipId = blip.attributes["r:embed"];
        var linkRelationshipId = blip.attributes["r:link"];
        if (embedRelationshipId) {
            return findEmbeddedImageFile(embedRelationshipId);
        } else if (linkRelationshipId) {
            var imagePath = relationships.findTargetByRelationshipId(linkRelationshipId);
            return {
                path: imagePath,
                read: files.read.bind(files, imagePath)
            };
        } else {
            return null;
        }
    }

    function readImageData(element) {
        var relationshipId = element.attributes['r:id'];

        if (relationshipId) {
            return readImage(
                findEmbeddedImageFile(relationshipId),
                element.attributes["o:title"]);
        } else {
            return emptyResultWithMessages([warning("A v:imagedata element without a relationship ID was ignored")]);
        }
    }

    function findEmbeddedImageFile(relationshipId) {
        var path = uris.uriToZipEntryName("word", relationships.findTargetByRelationshipId(relationshipId));
        return {
            path: path,
            read: docxFile.read.bind(docxFile, path)
        };
    }

    function readImage(imageFile, altText) {
        var contentType = contentTypes.findContentType(imageFile.path);

        var image = documents.Image({
            readImage: imageFile.read,
            altText: altText,
            contentType: contentType
        });
        var warnings = supportedImageTypes[contentType] ?
            [] : warning("Image of type " + contentType + " is unlikely to display in web browsers");
        return elementResultWithMessages(image, warnings);
    }

    function undefinedStyleWarning(type, styleId) {
        return warning(
            type + " style with ID " + styleId + " was referenced but not defined in the document");
    }
}


function readNumberingProperties(styleId, element, numbering) {
    var level = element.firstOrEmpty("w:ilvl").attributes["w:val"];
    var numId = element.firstOrEmpty("w:numId").attributes["w:val"];
    if (level !== undefined && numId !== undefined) {
        return numbering.findLevel(numId, level);
    }

    if (styleId != null) {
        var levelByStyleId = numbering.findLevelByParagraphStyleId(styleId);
        if (levelByStyleId != null) {
            return levelByStyleId;
        }
    }

    // Some malformed documents define numbering levels without an index, and
    // reference the numbering using a w:numPr element without a w:ilvl child.
    // To handle such cases, we assume a level of 0 as a fallback.
    if (numId !== undefined) {
        return numbering.findLevel(numId, "0");
    }

    return null;
}

var supportedImageTypes = {
    "image/png": true,
    "image/gif": true,
    "image/jpeg": true,
    "image/svg+xml": true,
    "image/tiff": true
};

var ignoreElements = {
    "office-word:wrap": true,
    "v:shadow": true,
    "v:shapetype": true,
    "w:annotationRef": true,
    "w:bookmarkEnd": true,
    "w:sectPr": true,
    "w:proofErr": true,
    "w:lastRenderedPageBreak": true,
    "w:commentRangeStart": true,
    "w:commentRangeEnd": true,
    "w:del": true,
    "w:footnoteRef": true,
    "w:endnoteRef": true,
    "w:pPr": true,
    "w:rPr": true,
    "w:tblPr": true,
    "w:tblGrid": true,
    "w:trPr": true,
    "w:tcPr": true
};

function emptyResultWithMessages(messages) {
    return new ReadResult(null, null, messages);
}

function emptyResult() {
    return new ReadResult(null);
}

function elementResult(element) {
    return new ReadResult(element);
}

function elementResultWithMessages(element, messages) {
    return new ReadResult(element, null, messages);
}

function ReadResult(element, extra, messages) {
    this.value = element || [];
    this.extra = extra || [];
    this._result = new Result({
        element: this.value,
        extra: extra
    }, messages);
    this.messages = this._result.messages;
}

ReadResult.prototype.toExtra = function() {
    return new ReadResult(null, joinElements(this.extra, this.value), this.messages);
};

ReadResult.prototype.insertExtra = function() {
    var extra = this.extra;
    if (extra && extra.length) {
        return new ReadResult(joinElements(this.value, extra), null, this.messages);
    } else {
        return this;
    }
};

ReadResult.prototype.map = function(func) {
    var result = this._result.map(function(value) {
        return func(value.element);
    });
    return new ReadResult(result.value, this.extra, result.messages);
};

ReadResult.prototype.flatMap = function(func) {
    var result = this._result.flatMap(function(value) {
        return func(value.element)._result;
    });
    return new ReadResult(result.value.element, joinElements(this.extra, result.value.extra), result.messages);
};

ReadResult.map = function(first, second, func) {
    return new ReadResult(
        func(first.value, second.value),
        joinElements(first.extra, second.extra),
        first.messages.concat(second.messages)
    );
};

function combineResults(results) {
    var result = Result.combine(_.pluck(results, "_result"));
    return new ReadResult(
        _.flatten(_.pluck(result.value, "element")),
        _.filter(_.flatten(_.pluck(result.value, "extra")), identity),
        result.messages
    );
}

function joinElements(first, second) {
    return _.flatten([first, second]);
}

function identity(value) {
    return value;
}

export {
    createBodyReader,
    readNumberingProperties as _readNumberingProperties
}
